1. Field of the Invention
The present invention relates to an air conditioner for air conditioning an interior, and in particular, to an air conditioner equipped with a solar battery which generates electric power by using sunlight as an energy source and supplies the generated electric power to a commercial electric power source.
2. Description of the Related Art
An air conditioner which air conditions an interior effects heat exchange with a ryefrigerant so as to operate in various operation modes such as, for example, "heating mode", "cooling mode", "dry mode", and "automatic operation mode" in which a set temperature and the temperature at the time of the start of operation are compared and one of the heating mode and the cooling mode are automatically selected. In this type of air conditioner, various operation settings such as operate/stop, operation mode setting, operation condition setting and the like can be carried out by remote operation by using a remote control which is an accessory of the air conditioner.
A so-called solar air conditioner which uses solar energy as power has been developed as the above-described type of air conditioner (see, for example, U.S. patent application Ser. No. 5,375,429). In this solar air conditioner, the power generated in accordance with the sunlight absorbed by a solar cell is used as the power of the air conditioner. Further, because the generated power is affected by the weather and the time of day, the solar air conditioner is used together with a commercial power source which is used conventionally. The allocation of the use of power generated from sunlight and the use of power from the commercial power source is controlled in accordance with the amount of power generated from sunlight, so that stable air conditioning operation can be guaranteed.
In the solar air conditioner having the above-described structure, the power generated by sunlight can only be used for the solar air conditioner. Therefore, when the solar air conditioner is not being operated or the like, regardless of the energy generating capability, power from sunlight cannot be used effectively.
As a result, supplying the power generated by the solar air conditioner to a general commercial power source has been proposed. Such a solar air conditioner has a power source supplying system which supplies the power generated from sunlight as commercial power, and uses commercial power together with the power generated from sunlight. In this way, the power generated from sunlight can be used effectively.
However, when the power generated from sunlight is supplied as commercial power, in order to monitor the amount of supplied power, an expensive measuring device is needed. Further, even if the solar generator includes a function for displaying the power generating state, the power generating state cannot be verified easily because the solar generator is located outside (i.e., at the exterior).
Because the conventional solar generator generates a relatively large amount of power, the devices for managing and controlling the generated power are relatively large. As compactness of air conditioners used for ordinary households is aimed for, if the solar generator which is formed integrally with the air conditioner is large, installation will be difficult. In the solar generator, the frequency, voltage and phase of the generated power must accurately match those of the commercial power. Further, in order to prevent overloading of the solar generator, interruption of the commercial power source must be accurately detected. Carrying out these detections and controls individually results in the structure of the solar generator becoming complex and in the solar generator becoming large.
When the solar generator is controlled by using the commercial power source, at times when the commercial power source is interrupted or the like, operation of the solar generator is stopped, and appropriate self-monitoring of the solar generator is not possible.
In a case in which, for example, there is a room which is to always be kept at a predetermined temperature or humidity, the consumed power from the commercial power source may vary due to the weather or the time of day so that electricity costs cannot be estimated and unforeseen expenses may result. Accordingly, a solar air conditioner which can furnish power only by solar energy is desirable. However, in order to realize such a solar air conditioner, a solar cell of an extremely large surface area would be required, which is impractical.